1. Field of the Invention
The present invention relates to a leather-like sheet material having an excellent flexibility, drape and moisture permeability, as well as a good appearance with smooth and high-quality feeling resembling natural leather, and being most suitable for grain-type apparels, various gloves, soft sports shoes and similar uses, and a process for its production.
2. Description of the Related Art
Known grain-type leather-like materials having excellent flexibility and moisture permeability include laminates of a fibrous base layer containing a porous elastic polymer and a porous coating layer principally comprising an elastic polymer or non-porous coating layer, and those comprising the former and further a layer of a non-porous coating layer on the surface of the porous coating layer. To obtain the porous coating layer for the above purpose, there are available a wet coagulation process which comprises treating an elastic polymer solution with a non-solvent for the polymer to coagulate it into a porous structure, a process which comprises preparing a composition by mixing an elastic polymer solution with readily extractable fine particles, e.g. salts, starch and gelatin, applying the composition on a base, followed by drying, and then extracting off the fine particles, a process which comprises kneading an elastic polymer with the above readily extractable fine particles, forming the obtained blend into a sheet and then extracting off the fine particles, a dry foaming process and the like.
Besides, Japanese Patent Application Laid-open Nos. 91279/1990, 169777/1990 and 307987/1990 propose a process which comprises forming on the surface of a wet-formed finely porous layer a polyurethane resin layer containing fine particles of a water-soluble natural polymer such as gelatin or starch and then dissolving off the water-soluble fine particles, to form a porous coating layer.
Various leather-like sheet materials having good flexibility and moisture permeability have been proposed, but none of them is suited for preparing high-quality grain-type apparels and various gloves that require excellent flexibility, drape and moisture permeability, as well as appearance with high-quality feeling. That is, with the above process of providing a surface layer of a wet-formed porous film, obtaining a smooth surface with the wet-formed film alone requires a large thickness of the film, thereby impairing the hand, while providing a finishing layer of a non-porous dry-formed film on the wet-formed porous film hardens the surface layer, whereby the surface layer tends to become ill balanced with the base layer and the resulting product loses the feeling of an integral body. On the other hand, with the above dry process of providing a non-porous or porous film, which can be relatively thin, the resulting articles lack a high-quality feeling on their surface and have an insufficient flexibility and drape for apparels and various gloves, as well as insufficient moisture permeability. With the above process of forming on the surface of a wet-formed finely porous layer a polyurethane resin layer containing fine particles of a water-soluble natural polymer and then dissolving off the water-soluble fine particles, the obtained wet-formed finely porous layer has a large thickness and a large pore size due to the water-soluble fine particles having a large particle diameter, thereby showing too poor flexibility and drape, as well as too low moisture permeability, to be used for thin-type apparels and various gloves.
Accordingly, an object of the present invention is to solve the above problems and provide a leather-like sheet material having an excellent flexibility and drape, a high moisture permeability of at least 4,000 g/m.sup.2 .multidot.24 hr and a smooth appearance with high-quality feeling resembling that of natural leather.
Another object of the present invention is to provide a process for producing the above leather-like sheet material.